Determining relative spatial information between vehicles

ABSTRACT

A method for determining relative spatial information between a first vehicle and a second vehicle, the method including monitoring a communication channel at the first vehicle and receiving a current communication signal sent by the second vehicle on the communication channel. The current communication signal is received at a received power level. A relative position between the first vehicle and the second vehicle is calculated. Input to the calculating includes an actual or estimated transmitted power level, and the received power level.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation of Application of U.S. patent application Ser.No. 11/029,890 filed Jan. 5, 2005, which is incorporated herein, byreference, in its entirety.

BACKGROUND

The present disclosure relates generally to determining relative spatialinformation between vehicles and, in particular, to the use of wirelesscommunication information and characteristics to determine a relativeposition between vehicles.

Many Active Safety (AS) and Driver Assistance (DA) systems requirerelative position with respect to neighboring vehicles in order toprotect or assist the occupants of the equipped vehicle. For example, anadaptive cruise control system utilizes a range measurement from theequipped, or host, vehicle to the lead vehicle to assist the driver ofthe host vehicle in maintaining a distance between the vehicles. In thecase of adaptive cruise control, the host vehicle is equipped with aradar, lidar, or vision sensor to detect vehicles ahead. Other systemsmay utilize sensors mounted on the sides of the vehicle or in theroadway to obtain a relative position measurement between vehicles.Another method of determining relative position between vehiclesinvolves the exchange of each vehicle's location as determined by aGlobal Navigation Satellite System (GNSS) receiver. This method may beutilized when both vehicles are equipped with a GNSS device. Examples ofGNSS devices include a Global Positioning System (GPS) and a Galileoreceiver.

BRIEF DESCRIPTION

According to one aspect of the invention, a method is provided fordetermining relative spatial information between a first vehicle and asecond vehicle using received signal strength (RSS). The method includesmonitoring a communication channel at the first vehicle and receiving acurrent communication signal from the second vehicle on thecommunication channel. The current communication signal is received at areceived power level. A distance between the first vehicle and thesecond vehicle is calculated. Input to the calculating includes, amongother things, an actual or estimated transmitted power level, and thereceived power level.

In another aspect of the invention, a system is provided for determiningrelative spatial information between a first vehicle and a secondvehicle. The system includes a receiver on the first vehicle formonitoring a communication channel. The system also includes a processorfor executing instructions to implement a method. The method includesmonitoring the communication channel and receiving a currentcommunication signal from the second vehicle on the communicationchannel. The current communication signal is received at a receivedpower level. A distance between the first vehicle and the second vehicleis calculated. Input to the calculating includes an actual or estimatedtransmitted power level, and the received power level.

In yet another aspect of the invention, a computer program product isprovided for determining relative spatial information between a firstvehicle and a second vehicle. The computer program product includes astorage medium readable by a processing circuit and storing instructionsfor execution by the processing circuit for performing a method. Themethod includes monitoring a communication channel and receiving acurrent communication signal from the second vehicle on thecommunication channel. The current communication signal is received at areceived power level. A distance between the first vehicle and thesecond vehicle is calculated. Input to the calculating includes anactual or estimated transmitted power level, and the received powerlevel.

In a further aspect of the invention, a method is provided fordetermining location information. The method includes receiving pathloss model parameters at a first vehicle. The path loss model parameterscorrespond to one or more communication channels utilized by surroundingvehicles. Communication signals are received at the first vehicle. Thecommunication signals are received via one or more of the communicationchannels from three or more of the surrounding vehicles. Thecommunication signals include GNSS coordinates corresponding to each ofthe three or more surrounding vehicles. Range measurements between thefirst vehicle and the three or more surrounding vehicles are estimated.The estimating is responsive to the path loss model parameters and toestimated signal strengths associated with the communication signals. Analgorithm is executed to determine estimated GNSS coordinates for thefirst vehicle. Input to the algorithm includes the GNSS coordinatescorresponding to each of the three or more surrounding vehicles and tothe range measurements.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures, which are meant to be exemplaryembodiments, and wherein the like elements are numbered alike:

FIG. 1 is a block diagram of a host vehicle and a neighboring vehicle inaccordance with exemplary embodiments of the present invention;

FIG. 2 is a process flow that may be utilized by exemplary embodimentsof the present invention to determine relative spatial informationbetween vehicles;

FIG. 3 is a process flow that may be utilized by alternate exemplaryembodiments of the present invention to determine relative spatialinformation between vehicles;

FIG. 4 is a block diagram of a cluster of vehicles in accordance withexemplary embodiments of the present invention;

FIG. 5 is a block diagram of a cluster of vehicles transmitting distanceand path loss exponents in accordance with exemplary embodiments of thepresent invention;

FIG. 6 is a block diagram of a GNSS-unequipped (GNSS-U) vehicle in acluster of vehicles calculating a distance of separation from othervehicles within the cluster according to exemplary embodiments of thepresent invention; and

FIG. 7 is a block diagram of a GNSS-U vehicle in a cluster of vehiclescalculating GNSS coordinates of the GNSS-U vehicle in accordance withexemplary embodiments of the present invention.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention include a technique forutilizing transmit power, signal strength, Doppler shift and vehiclesensor information to obtain an estimated relative position between ahost vehicle and one or more neighboring vehicles. The transmissionpower, signal strength and Doppler shift are obtained from a wirelesscommunication device on the host vehicle without requiring any specialcooperation from the neighboring vehicles. To implement exemplaryembodiments of the present invention, the host vehicle is equipped witha wireless communication device that can estimate received signalstrength (RSS) and optionally, the Doppler shift of a signal receivedfrom another communication device on a neighboring vehicle. Informationtransmitted across the wireless communication link may be utilized toimprove the relative positioning estimates between the host vehicle andone or more neighboring vehicles.

When two devices communicate wirelessly, the transmitter in a wirelesscommunication device sends data at a known transmission power level,P_(t), and the receiver in a wireless communication device receives thedata at a measured received power level, P_(r). A free space losswireless communication model, or equation, such as

P _(t) /P _(r)=(4πd/λ)^(p),

may be utilized to indicate that the ratio between the two power levelsis a function of distance, d, and path loss exponent, p, for a fixed(and known) wavelength, λ. In exemplary embodiments of the presentinvention, vehicles with wireless communication devices utilize a freespace loss wireless communication model, such as the one above with p=2,to estimate the distance between a host vehicle and a neighboringvehicle. The transmitting communication device transmits information atthe fixed transmission power level, P_(t). The receiving communicationdevice estimates the distance between the vehicles based on thetransmission power level, P_(t), and the received power level, P_(r),according to a free space loss equation such as the one above. Anywireless communication path loss model may be utilized (e.g., afree-space path loss communication model and a two-ray path losscommunication model) by exemplary embodiments of the present inventionto determine an estimated distance, or relative position, between thevehicles.

FIG. 1 depicts a host vehicle 102 (or first vehicle) and a neighboringvehicle 104 (or second vehicle), both containing a wirelesscommunication device 108. The host vehicle 102, as referred to herein,is the vehicle that is calculating the range, and the neighboringvehicle 104 is the vehicle that is continuously transmitting acommunication signal that is received at the host vehicle 102. Thecommunication signals may be classified as earlier communication signals(that were received at an earlier point it time), current communicationsignals (that were the last received communications signals) and latercommunication signals (that will be received at a point in time in thefuture). In exemplary embodiments of the present invention, the hostvehicle 102 performs both the host vehicle processing described herein(e.g., calculating a range) as well as the neighboring vehicleprocessing (e.g., transmitting a communication signal) described herein.Similarly, the neighboring vehicle 104 may perform both the host vehicleprocessing described herein (e.g., calculating a range) as well as theneighboring vehicle processing (e.g., transmitting a communicationsignal) described herein. The host vehicle processing may be performedby hardware and/or software that is located within and/or remote to thehost vehicle 102. Similarly, the neighboring vehicle processing may beperformed by hardware and/or software that is located within and/orremote from the neighboring vehicle 104. Data from the wirelesscommunication devices 108 is utilized to estimate a range 106 (ordistance) between the host vehicle 102 and the neighboring vehicle 104.The host vehicle 102 may be an automobile, an over the highway tractor,a boat, a motorcycle, a pedestrian, and the like. Similarly, theneighboring vehicle 104 may be an automobile, an over the highwaytractor, a boat, a motorcycle, a pedestrian, and the like.

The host vehicle 102 and the neighboring vehicle 104 both include awireless communication device 108. The wireless communication devices108 may include transmitters and receivers and may be implemented by anydevice capable of wireless communications including, but not limited towireless fidelity (WiFi), infrared (IR), radio frequency (RF) and anyInstitute of Electrical and Electronics Engineers (IEEE) 802.11technology. The host vehicle 102 and the neighboring vehicle 104 mayutilize different communication devices as long as the devices have thecapability of communicating in a wireless fashion with each other.

In a multi-channel communications environment, the host vehicle 102 andneighboring vehicles 104 may switch from a control channel to a servicechannel to exchange messages enabling the estimation of range (orrelative position) between vehicles. This switch may be required due tothe communication protocol being followed or may be done to improve theaccuracy and reliability of the power or range estimates. In systemswhere vehicles are periodically broadcasting information, channelswitching or special messages specifically for the purposes of rangingmay not be required or may be limited in number as long as the hostvehicle 102 monitors the channel used for broadcasting.

FIG. 2 depicts a process flow utilized by exemplary embodiments of thepresent invention where the host vehicle 102 estimates range basedsolely on the received power level and an assumption of the transmittedpower level from a neighboring vehicle 104. This scenario requires nocooperation from the neighboring vehicle 104 (beyond transmitting asignal) and provides an estimate of the range 106 between the hostvehicle 102 and the neighboring vehicle 104 for transmissions receivedat the host vehicle 102 from the neighboring vehicle 104. Thecalculation of the range 106 may be augmented by a range-ratecalculation when the host vehicle 102 estimates the Doppler shift of themessage from the neighboring vehicle 104. Over a number of samples, theconfidence in the range and/or range-rate estimates may increase,compensating for the effects of fading in a mobile environment. At step202, the process starts and at step 204 a neighboring vehicle 104 sendsa wireless communication signal via a transmitter in the wirelesscommunication device 108 located on the neighboring vehicle 104. At step206, a receiver in the wireless communication device 108 on the hostvehicle 102, that has been monitoring a communication channel, receivesthe current wireless communication signal from the neighboring vehicle104. The current wireless communication signal is received by thereceiver in the wireless communication device 108 on the host vehicle102 at a received power level. After step 206 is completed, steps 208and 214 are initiated (in parallel as depicted in FIG. 2 or in serial).

At step 208 in FIG. 2, the host vehicle 102 estimates the received powerlevel of the current communication signal and at step 210, the hostvehicle 102 estimates the range 106 (or relative position) between theneighboring vehicle 104 and the host vehicle 102. An integrated circuit,or other computing device, on the host vehicle 102 estimates the range106 using the received power level and the assumed transmitted powerlevel of the sending neighboring vehicle 104 (e.g., using a free spaceloss wireless communication model). In alternate exemplary embodimentsof the present invention, an actual transmission power level is utilizedwhen the neighboring vehicle 104 transmits the transmitted power levelto the host vehicle 102 and the host vehicle 102 has the capability oftranslating a message from the neighboring vehicle 104 when the messageis encoded in a message set. The neighboring vehicle 104 may encode thetransmitted power in the transmission used by the host vehicle 102 forcalculation of range. Alternatively, the neighboring vehicle 104 mayencode the transmitted power in transmissions before or after thetransmission used by the host vehicle 102 for ranging. Thesetransmissions may occur on a different communication channel than thetransmission being used by the host for ranging. At step 214, the hostvehicle 102 estimates the Doppler shift of the current wirelesscommunication signal from the neighboring vehicle 104. At step 216, thehost vehicle 102 estimates a range rate using the Doppler estimate. Oncesteps 210 and 216 are completed, the loop ends at step 212 andprocessing continues at step 204 when the neighboring vehicle 104transmits another wireless communication signal.

FIG. 3 depicts a process flow for alternate exemplary embodiments of thepresent invention. The process depicted in FIG. 3 includes a relativepositioning module 308. The relative positioning module 308 utilizeshost vehicle information 304 from the host vehicle 102 such as speed,yaw rate, object detection sensor data, antenna model and GNSS position,along with similar neighboring vehicle information 302 from theneighboring vehicle 104 to improve the relative position estimates(e.g., range and range-rate estimates between vehicles 312). Theneighboring vehicle 104 communicates its communication characteristics,such as antenna model and transmission power level, to the host vehicle102 in order to improve the relative spatial determination. The relativepositioning module 308 utilizes host vehicle information 304,neighboring vehicle information 302 and the estimated communicationparameters 310 (e.g., wavelength, outside air temperature, estimatedtransmission power level) to create the range and range-rate estimatesbetween vehicles 312. In addition, the host vehicle information 304 andneighboring vehicle information 302 may be utilized by the relativepositioning module 308 to update the estimated communication parameters310.

During times when the object detection sensors of the host vehicle 102have reached their limitation, exemplary embodiments of the presentinvention may provide some level of relative positioning between thehost vehicle 102 and the neighboring vehicle 104 using the estimatedcommunication parameters 310 as input to the relative positioning module308. At system start up, default values may be entered into theestimated communication parameters 310 including sensed conditions suchas outside air temperature, humidity, and vehicle speed as well as othercommunication parameters utilized by the relative positioning module308. Relative positioning between the host vehicle 102 and theneighboring vehicle 104 may be improved when the object detectionsensors are functioning at an optimum level.

When the object detection sensors are functioning at an optimum level,information from the object detection sensors relating to the range andrange-rate between vehicles will be utilized to calculate the range andrange-rate estimates between vehicles 312. In exemplary embodiments ofthe present invention, the results of this calculation will be comparedto the results of the estimation that took place in step 210 andutilized to improve the estimation of the relative position between thevehicles. In addition, the range and range rate information from theobject detection sensors may be utilized by the relative positioningmodule 308 to update the estimated communication parameters 310. Theseestimated communication parameters 310 may be fixed or dependent ontime, location, vehicle, etc.

When the object detection sensors are not functioning at an optimallevel (e.g., extreme glare into cameras, limited field of view forradar), steps 210 and 216 in FIG. 2 will be able to estimate range andrange-rate using models in the relative positioning module 308 thatutilize the estimated communication parameters 310 estimated duringearlier operation.

As depicted in FIG. 3, the relative spatial information that iscalculated based on the transmitted and received power levels, may beutilized as a back up or supplement to other relative positiondetermination or object detection systems. In this manner, the ActiveSafety (AS) and/or Driver Assistance (DA) systems may continue tooperate for some period of time, providing the same or a sublevel ofinformation, in the event that other relative position determination orobject detection systems are not fully functioning or are limited intheir ability. In addition, the calculated relative spatial informationmay be utilized to verify that the other relative position determinationor object detection systems are providing valid data.

Other exemplary embodiments of the present invention include the abilityto filter estimates over time in order to bound relative spatialposition conclusions based on previous estimates. In this manner, anestimated spatial position that is an anomaly may be discarded or usedwith a lower confidence value. In addition, previous relative positionsat previous points in time may be utilized to predict future relativepositions.

In other exemplary embodiments of the present invention, the hostvehicle 102 and the neighboring vehicle 104 transmit estimated relativespatial information to each other so that they may observe each other'sindividual estimates. In this manner, the host vehicle 102 may verifyits estimated relative spatial information by comparing it to theestimated relative spatial information received from the neighboringvehicle 104. Similarly, the neighboring vehicle 104 may verify itsestimated relative spatial information by comparing it to the estimatedrelative spatial information received from the host vehicle 102.Further, advanced filters may be utilized to estimate headingdifferences and vehicle maneuvers.

Other exemplary embodiments of the present invention include the abilityto utilize information from multiple neighboring vehicles 104 to improvethe range and range rate estimates made by the host vehicle 102. Forexample, GNSS-equipped (GNSS-E) vehicles in a cluster of vehicles thatincludes other GNSS-E vehicles, and optionally, GNSS-unequipped (GNSS-U)vehicles may be utilized to determine estimated relative positionsbetween the vehicles. As used herein, the term “cluster of vehicles”refers to any set or subset of vehicles located in a geographic area.The term “GNSS-E vehicle”, as used herein, refers to a vehicle that hasGNSS and/or inertial measurement and/or dead-reckoning systems and candetermine its absolute GNSS coordinates using GNSS signals or canpredict its current position coordinates using an inertial measurementand/or dead-reckoning system. In addition, the term “GNSS-U vehicle”, asused herein, refers to a vehicle that at times may not be able todetermine its position coordinates either due to lack of onboard GNSSsystems, lack of access to GNSS signals and/or lack of inertialmeasurement and/or dead-reckoning systems.

Path loss exponent values are estimated for the wireless channel betweenall possible pairs of GNSS-E vehicles within direct communication rangein a cluster of vehicles. In a given region, the path loss exponentvalues may not vary significantly. Therefore, these values may beutilized to provide an estimate of the wireless channel in the regionand stored as an estimated communication parameter 310 for use by therelative positioning module 308. The GNSS-E vehicles transmit the pathloss exponent values to GNSS-U vehicles. The GNSS-U vehicles use thepath loss exponent values as input to the relative positioning module308 for characterizing the wireless channel between them and theneighboring GNSS-E vehicles. The relative positioning modules 308utilize the path loss exponent values to determine the distance of aGNSS-U vehicle from other GNSS-E vehicles in the cluster and todetermine approximations of GNSS coordinates relative to those of otherGNSS-E vehicles in the cluster.

Some GNSS-E vehicles must be present in the cluster of vehicles so thatthe GNSS-U vehicles can utilize received signal strength (RSS) basedranging (e.g., using the path loss exponent values) and trilaterationtechniques to determine their GNSS coordinates relative to those ofGNSS-E vehicles. Theoretically, a GNSS-U vehicle requiresdistance-of-separation values from only three non-collinear GNSS-Evehicles to accurately determine its GNSS coordinates. However, becausethe distance values may have errors, a GNSS-U vehicle may be able tomore accurately determine its GNSS coordinates by using rangingmeasurements from more than three non-collinear GNSS-E vehicles.

The wireless communication path loss model described previously may beenhanced by more detailed characterizations of the wireless channelbetween two vehicles so that a relationship between the RSS values andthe inter-vehicular distances can be established. Vehicles may utilize adatabase of predefined communication parameters 314 including path lossmodels and/or path loss exponents for a range of operationalenvironments (such as rural, semi-urban, urban, dense urban, etc). Thedatabase 314 is accessible by the host vehicle processing describedherein and the database 314 may be located within the vehicle or remotefrom the vehicle. Alternatively, portions of the database 314 may belocated on the vehicle and other portions located remote to the vehicle.The relative positioning module 308 can then use these models to derivea relative position estimate. In a cluster of mobile vehicles, it may bemore difficult for a GNSS-U vehicle to characterize the surroundingwireless channel. However, pairs of GNSS-E vehicles can do so easily.Exemplary embodiments of the present invention use pairs of GNSS-Evehicles to characterize the wireless channel in the cluster and tobroadcast this information to all the GNSS-U vehicles. Based on thisreal-time characterization of the wireless channel in the cluster,GNSS-U vehicles in the cluster may be able to establish a more accuraterelationship for determining relative distances using signal strengthsof the received information packets.

FIG. 4 is a block diagram of a cluster of vehicles that includes GNSS-Eand GNSS-U vehicles in accordance with exemplary embodiments of thepresent invention. FIG. 4 includes five GNSS-E nodes (node 1 401, node 2402, node 3 403, node 4 404 and node 5 405) each corresponding to alocation of a different GNSS-E vehicle and one GNSS-U node (node 6 406)corresponding to the location of a GNSS-U vehicle. In addition, FIG. 4indicates a distance (e.g., d1, d2 and d3) and a path loss exponentvalue (e.g., p1, p2 and p3) between each pair of GNSS-E nodes. Inexemplary embodiments of the present invention, all the GNSS-E vehiclepairs in the cluster within direct communication range utilize signalstrength based ranging techniques as described above to estimate thepath loss exponent values as depicted in FIG. 4. The host vehicle 102depicted in FIG. 1 may be any or all of the GNSS-E vehicles or any orall of the GNSS-U vehicles. Similarly, the neighboring vehicle 104depicted in FIG. 1 may be any or all of the GNSS-E vehicles or any orall of the GNSS-U vehicles.

FIG. 5 is a block diagram of a cluster of vehicles transmitting distanceand path loss exponent values in accordance with exemplary embodimentsof the present invention. Once the GNSS-E vehicle pairs in the clusterwithin direct communication range are identified, the GNSS-E vehiclestransmit information packets containing their current GNSS coordinatesand power of the transmitted packet at the output at the antennae on thevehicle. Note that the vehicles need not transmit just one informationpacket but instead may transmit a number of packets to allow averagingout of small scale fading effects. The information packets are broadcastto both GNSS-E and GNSS-U vehicles in the cluster.

All of the GNSS-E vehicles in the cluster exchange information packetsand determine distances of separation between themselves as well as pathloss exponent values for individual local wireless channels. Uponreceipt of the information packets by the GNSS-E vehicles in thecluster, they calculate the distances between them and the transmittingvehicle using respective GNSS coordinates. The total path loss iscalculated for each pair of GNSS-E vehicles in the cluster. Path losscan be derived as the transmission power level, P_(t), minus thereceived power level, P_(r). Next, the receiving GNSS-E vehiclescalculate the path loss exponent values (using previously calculateddistance and path loss values) for the wireless channel between them andthe transmitting vehicle. Generally, in a given region, the path lossexponent values may not vary significantly. Thus, these values canprovide an estimate of the wireless channel within the cluster.

The receiving GNSS-E vehicles broadcast these path loss exponent values(along with other pertinent information such as the GNSS coordinates,orientations, and heading of each individual pairs of vehicles) toGNSS-U vehicles within the cluster. The GNSS-U vehicles may establish adatabase of path loss exponent values that are continuously updated overtime. FIG. 6 is a block diagram of a GNSS-U vehicle in a cluster ofvehicles calculating a distance of separation from other vehicles withinthe cluster according to exemplary embodiments of the present invention.Based on the signal strengths of information packets received fromneighboring GNSS-E vehicles and the onboard database of path lossexponent values, the GNSS-U vehicle at node 6 406 calculates distancesof separation between itself and neighboring GNSS-E vehicles.

FIG. 7 is a block diagram of a GNSS-U vehicle in a cluster of vehiclescalculating GNSS coordinates of the GNSS-U vehicle in accordance withexemplary embodiments of the present invention. The GNSS-U vehicles cannow identify GNSS-E vehicles in the cluster within direct communicationrange (so as to determine their GNSS coordinates relative to the GNSScoordinates of GNSS-E vehicles using RSS based ranging andtrilateration) and use the onboard database of path loss exponent valuesto determine appropriate path loss exponents for wireless channelsbetween them and each of their neighboring GNSS-E vehicles. The GNSS-Uvehicle may perform trilateration (circles with positions of GNSS-Evehicles as center and distances of separation with GNSS-less vehicle asradii) to determine its position relative to GNSS coordinates of itsneighboring GNSS-E vehicles. Ideally, the point of intersection of allthe circles, as shown in FIG. 7, gives the GNSS coordinates of theGNSS-U vehicle. When the circles do not intersect at one point,techniques known to those skilled in the art will be applied to resolvethe GNSS coordinates.

Alternate exemplary embodiments may allow GNSS-E vehicles to becomeGNSS-U vehicles during outages and maintain relative spatial measurementaccuracy. If a cluster of GNSS-E vehicles have over time estimated pathloss exponents, the same vehicles may use the previous estimates of pathloss exponents during a period of time when GNSS information may not beavailable (e.g., tree cover or vehicle entry into a tunnel) in any orall of the vehicles. The use of previous path loss exponent measurementscan provide a better path loss model for determining relative spatialinformation between the set of vehicles.

The alternate exemplary embodiment described in reference to FIGS. 4 to7 may be utilized when the host vehicle 102 and neighboring vehicle 104are part of a cluster of vehicles that contain GNSS devices. One, bothor neither of the host vehicle 102 and the neighboring vehicle 104 arerequired to have a GNSS device to use this alternate embodiment. Usingthe predicted path loss exponent values may result in a better estimateof the relative position of the neighboring vehicle 104 with respect tothe host vehicle 102 when compared to the path loss models described inreference to FIGS. 2-3. By using the predicted path loss exponent values(that may be more accurate than free-space path loss models, two raypath loss models, or other generalized path loss models), the GNSS-Uvehicles derive a relationship between the signal strength of receivedpacket(s) and the inter-vehicular distances. The GNSS-U vehicles thenuse this relationship to predict a distance between them and thetransmitting GNSS-E vehicles. In this manner, the overall performance ofthe RSS based ranging technique may be improved. This may directlytranslate into better performance of AS and DA systems, and indirectlytranslate to earlier introduction of the collision warning applicationin the vehicles.

Exemplary embodiments of the present invention may be utilized toincrease the accuracy of RSS based ranging measurements and thus lowerthe optimum number of ranging measurements required by GNSS-U vehiclesto determine GNSS coordinates. Also, since achieving a higherpenetration level for GNSS-E vehicles may not always be feasible, bylowering the requirements on the penetration level of GNSS-E vehicles,exemplary embodiments of the present invention may be utilized tofacilitate earlier adoption of various AS and DA applications.

Exemplary embodiments of the present invention may be utilized todetermine relative spatial information between vehicles using a vehiclecentered approach that focuses on ranging between two points (the hostvehicle 102 and the neighboring vehicle 104). In addition, a message setthat is standard to vehicle communication systems is utilized andtherefore, no specialized message set is required. The relative spatialinformation may be utilized to replace and/or augment existing rangesensors such as radar, lidar and GNSS.

As described above, the embodiments of the invention may be embodied inthe form of hardware, software, firmware, or any processes and/orapparatuses for practicing the embodiments. Embodiments of the inventionmay also be embodied in the form of computer program code containinginstructions embodied in tangible media, such as floppy diskettes,CD-ROMs, hard drives, or any other computer-readable storage medium,wherein, when the computer program code is loaded into and executed by acomputer, the computer becomes an apparatus for practicing theinvention. The present invention can also be embodied in the form ofcomputer program code, for example, whether stored in a storage medium,loaded into and/or executed by a computer, or transmitted over sometransmission medium, such as over electrical wiring or cabling, throughfiber optics, or via electromagnetic radiation, wherein, when thecomputer program code is loaded into and executed by a computer, thecomputer becomes an apparatus for practicing the invention. Whenimplemented on a general-purpose microprocessor, the computer programcode segments configure the microprocessor to create specific logiccircuits.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims. Moreover, the use of the terms first, second, etc. do not denoteany order or importance, but rather the terms first, second, etc. areused to distinguish one element from another.

1. A non-transitory computer-readable medium tangibly containingcomputer-executable instructions for determining relative spatialinformation between a first vehicle and a second vehicle, whereinexecution of the instructions by a processing circuit causes theprocessing circuit to execute the steps of: monitoring a communicationchannel at the first vehicle; receiving on the communication channel atthe first vehicle a communication signal originating from the secondvehicle at a fixed power level, wherein the communication signal asreceived defines a current communication signal at a received powerlevel; and calculating a relative position between the first vehicle andthe second vehicle, wherein input to the calculating includes an actualor estimated transmitted power level and the received power level. 2.The non-transitory computer-readable medium as set forth in claim 1,wherein calculating the relative position includes using a wirelesscommunication path loss model.
 3. The non-transitory computer-readablemedium as set forth in claim 1, wherein calculating the relativeposition is performed based on a past estimate of a wirelesscommunication path loss model parameter.
 4. The non-transitorycomputer-readable medium tangibly as set forth in claim 1, whereincalculating the relative position includes executing a free space pathloss wireless communication model.
 5. The non-transitorycomputer-readable medium tangibly as set forth in claim 1, whereincalculating the relative position includes executing a two-ray path losswireless communication model.
 6. The non-transitory computer-readablemedium tangibly as set forth in claim 1, wherein one or more of anearlier communication signal, the current communication signal and alater communication signal includes an estimated path loss exponentvalue, and input to the calculating further includes the estimated pathloss exponent value.
 7. The non-transitory computer-readable mediumtangibly as set forth in claim 1, wherein calculating the relativeposition between the first vehicle and the second vehicle is performedin conjunction with a Global Navigation Satellite System (GNSS) device.8. The non-transitory computer-readable medium tangibly as set forth inclaim 1, wherein execution of the instructions by the processing circuitcauses the processing circuit to execute the step of transmitting therelative position to one or more of an Active Safety system and a DriverAssistance system.
 9. The non-transitory computer-readable mediumtangibly as set forth in claim 1, wherein execution of the instructionsby the processing circuit causes the processing circuit to execute thestep of determining a range rate associated with the currentcommunication signal, wherein input to the determining includes aDoppler shift associated with the current communication signal.
 10. Thenon-transitory computer-readable medium tangibly as set forth in claim1, wherein input to calculating the relative position includes firstvehicle information.
 11. The non-transitory computer-readable mediumtangibly as set forth in claim 10, wherein calculating the relativeposition includes using the first vehicle information to filter orsmooth distance estimates.
 12. The non-transitory computer-readablemedium tangibly as set forth in claim 1, wherein one or more of anearlier communication signal, the current communication signal and alater communication signal includes second vehicle information.
 13. Thenon-transitory computer-readable medium tangibly as set forth in claim12, wherein calculating the relative position includes using the secondvehicle information to filter or smooth distance estimates.
 14. Thenon-transitory computer-readable medium tangibly as set forth in claim1, wherein one or more of an earlier communication signal, the currentcommunication signal and a later communication signal includes anestimate of the distance as calculated by the second vehicle.
 15. Thenon-transitory computer-readable medium tangibly as set forth in claim1, input to calculating the relative position includes an estimatedcommunication parameter.
 16. The non-transitory computer-readable mediumtangibly as set forth in claim 1, wherein one or more of an earliercommunication signal, the current communication signal and a latercommunication signal includes an actual transmitted power level and thevalue of the estimated transmitted power level is set to the actualtransmitted power level.
 17. The non-transitory computer-readable mediumtangibly as set forth in claim 1, wherein the first vehicle includes aGlobal Navigation Satellite System (GNSS) device for determining a GNSSposition of the first vehicle and wherein the input to calculating therelative position further includes the GNSS position of the firstvehicle.
 18. The non-transitory computer-readable medium tangibly as setforth in claim 1, wherein the first vehicle has access to a database ofpredefined communication parameters and the input to calculating therelative position further includes one or more of the predefinedcommunication parameters.
 19. The non-transitory computer-readablemedium tangibly as set forth in claim 1, wherein execution of theinstructions by the processing circuit causes the processing circuit toexecute the step of receiving the current communication signal by areceiver on the first vehicle.
 20. The non-transitory computer-readablemedium tangibly as set forth in claim 1, wherein execution of theinstructions by the processing circuit causes the processing circuit toexecute the step of determining a GNSS position of the first vehicle inresponse to the GNSS position of the second vehicle and to a path lossexponent value.